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Viruses: The unsung heroes of evolution

By Garry Hamilton

Mimivirus

(Image: SPL)

FEW aspects of evolution are harder to explain than the emergence of complexity. How did the first cell emerge from the primordial soup? How did natural selection come up with a marvel as complex as the human brain? The tree of life is full of similar riddles – great evolutionary advances whose origins defy easy explanation.

Since the discovery of DNA, biologists have insisted they have the answer&colon; complexity arises as the result of small errors that occur when genomes are copied and passed down the generations. Although individually small, these mutations can add up to enormous change across the vastness of time.

This view of evolution has held sway for about 50 years, but now biologists are sensing that it is missing a major element – viruses. For close to a century, these genetic parasites have been regarded as little more than a biological afterthought, notable mainly for their ability to cause death and disease. However, the era of genomics has unexpectedly revealed a much richer picture of viruses as a creative evolutionary force of unparalleled reach and power. “Everywhere you look, viruses seem to be playing a crucial role in evolution,” says Luis Villarreal, director of the Center for Virus Research at the University of California, Irvine. “I would argue that they are the most creative genetic entities that we know of.”

“Everywhere you look, viruses seem to be playing a crucial role in evolution”

Such revelations will come as a surprise to many. Viruses are generally seen as finely honed killing machines – pared-down packages of genetic information that exist solely to attack …